Field of the Invention
The present invention relates to a pulse width modulation (PWM) signal generating apparatus, a motor control apparatus, and a light scanning apparatus. For example, the present invention relates to a PWM signal generating apparatus, a motor control apparatus, and a light scanning apparatus which are mounted to an image forming apparatus such as a laser printer and a digital copying machine for forming an image by subjecting a photosensitive member to charging, exposure, and development with the use of electrophotography.
Description of the Related Art
An electrophotographic image forming apparatus includes a light scanning apparatus configured to emit a light beam, and irradiates a surface of a uniformly charged photosensitive member with the light beam corresponding to image data, to thereby form a latent image on the photosensitive member. The light scanning apparatus includes a sensor located in a predetermined position on a scanning line of the light beam, and detects a timing to emit the light beam corresponding to the image data based on a result of detecting the light beam with the use of the sensor. An image forming apparatus generates a PWM signal for driving a light source based on the image data with reference to the timing based on a detection result from the sensor, and controls the light scanning apparatus, to thereby form the latent image on the photosensitive drum. When an image is to be formed, an image resolution is determined by a drive resolution of a laser. In order to increase the image resolution, there is proposed a configuration using a parallel serial conversion circuit (see, for example, Japanese Patent Application Laid-Open No. 2009-137037). Further, control using the PWM signal is also used for control of a rotation speed of a motor or the like.
With a related-art method of generating a PWM signal, pattern data on a PWM signal is generated by the parallel serial conversion circuit. The parallel serial conversion circuit uses a shift operation of a flip-flop circuit (hereinafter referred to as “F/F”) inside a semiconductor, and hence it is easy to make an operating frequency relatively higher. The operating speed of the F/F needs to be increased in order to generate the PWM signal having a higher resolution, but the operating speed of the F/F is nearing an upper limit as well, and it is becoming more difficult to further increase the resolution.